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People who drink an excessive number of drinks will be impaired, even if they are heavy drinkers. Narcisa Palici / 500px/Getty Images
  • A new study found that when people with alcohol-use disorder consumed the equivalent of seven to eight drinks they showed impairment on fine motor and cognitive tasks.
  • This impairment was “more than double” what they experienced after consuming the smaller intoxicating amount of alcohol.
  • Heavy drinkers and people with AUD both reported feeling less impaired than the light drinkers.
  • Tolerance also does not reduce the damage that can be caused by alcohol, experts say.

While under some conditions, heavy drinkers may be better at “holding their liquor,” this is only true up to a certain level of alcohol intake, say researchers from the University of Chicago.

In a study published June 18 in Alcohol: Clinical and Experimental Research, they tested the effects of alcohol consumption on young adults with different patterns of alcohol use — light and heavy social drinkers, and those with alcohol use disorder (or AUD, previously known as alcoholism).

Researchers found that heavy drinkers and those with AUD showed less overall impairment on fine motor and cognitive tasks after consuming the equivalent of four to five drinks, compared to light drinkers.

This amount of alcohol is sufficient to produce a blood alcohol content (BAC) of 0.08-0.09%, the lower limit in the United States for drunk driving.

However, when people with AUD consumed the equivalent of seven to eight drinks — which researchers say is more in line with their usual drinking habits, and produces a BAC of around 0.13% — they showed impairment on both of those tasks.

In fact, this impairment was “more than double” what they experienced after consuming the smaller intoxicating amount of alcohol. Three hours after drinking, their performance on these tasks still hadn’t returned to their baseline level.

In addition, people with AUD had greater impairment after consuming the larger amount of alcohol than what light drinkers experienced after drinking the lesser amount.

“There’s a lot of thinking that when experienced drinkers (those with AUD) consume alcohol, they are tolerant to its impairing effects,” study author Andrea King, PhD, a professor of psychiatry and behavioral neuroscience at the University of Chicago, said in a news release.

“[Our study] supported that a bit, but with a lot of nuances,” she added. “When [young people with AUD] drank alcohol in our study at a dose similar to their usual drinking pattern, we saw significant impairments on both the fine motor and cognitive tests that was even more impairment than a light drinker gets at the intoxicating dose.”

Dr. Lawrence Weinstein, chief medical officer of American Addiction Centers, who was not involved in the new research, said the study highlights that technically, no one can “handle their liquor.”

“There may be a marked difference in the amount of alcohol at which someone becomes intoxicated, which is a worrying issue in itself, but ethanol, acetaldehyde and other metabolites are toxicants that will affect anyone who consumes alcohol despite the tolerance they’ve developed,” he told Healthline.

Tolerance also does not reduce the damage that can be caused by alcohol, he said, adding: “It is illogical to believe that one would remain unaffected by regular consumption [of alcohol].”

According to the Centers for Disease Control and Prevention, more than 140,000 people die from excessive alcohol use in the United States each year, making it the fourth-leading preventable cause of death in the country.

In addition, almost 30% of U.S. traffic fatalities in 2019 involved alcohol-impaired driving, reports the National Highway Traffic Safety Administration.

Over the long term, excessive alcohol use can increase the risk of high blood pressure, heart disease, stroke, liver disease, certain types of cancer and other health problems.

“[Alcohol is] costly to our society for so many reasons,” said King in the release. “I’m hoping we can educate people who are experienced high-intensity drinkers who think that they’re holding their liquor or that they’re tolerant and won’t experience accidents or injury from drinking.”

In the new study, researchers enrolled almost 400 young people, most in their 20s, with different drinking patterns:

  • light drinkers: consumed six or fewer drinks per week, with few binge drinking episodes
  • heavy drinkers: consumed at least 10 drinks per week, with one to five heavy drinking episodes during that time
  • drinkers with AUD: consumed 28 or more drinks per week (21 or more for women), with at least 11 heavy drinking episodes per month; they also had to meet two or more clinical criteria for AUD

Binge drinking means consuming five or more drinks within about two hours for men, and four or more drinks for women.

Participants underwent two rounds of testing, one after consuming a high alcohol dose (the equivalent of four to five drinks) and the other after consuming a placebo drink containing only 1% alcohol (to create a similar taste). Both contained a flavored drink mix.

Researchers told participants they would receive a drink containing alcohol, a stimulant, a sedative or a placebo. This was to reduce the effect that people’s expectations might have on the results.

Participants consumed each drink over a 15-minute period.

Before drinking the beverage, and 30, 60, 120 and 180 minutes after drinking, participants took a breathalyzer and completed two performance tasks.

One task involved inserting a grooved metal peg into randomly slotted holes; this measured fine motor skills. The other was a pencil-and-paper task designed to test cognitive skills.

At the 30- and 180-minute intervals, participants also reported how impaired they felt.

Heavy drinkers and people with AUD both reported feeling less impaired than the light drinkers.

In addition, these two groups showed less overall alcohol impairment on the fine motor and cognitive tests; although all groups had similar impairment on the fine motor test at the 30-minute interval.

The performance of heavy drinkers and people with AUD returned to baseline more quickly than that of light drinkers, suggesting they may have greater alcohol tolerance.

However, people with AUD often drink more than four or five drinks in a session. So researchers asked a subset of participants with AUD to repeat the tasks after consuming the equivalent of seven to eight drinks.

At this dose, they had more than double the impairment they experienced at the lower intoxicating dose. Their performance also did not return to baseline during the testing, even after three hours.

They also experienced greater impairment from that higher dose than light drinkers did after the lower intoxicating dose.

“I was surprised at how much impairment that group had to that larger dose, because while it’s 50% more [alcohol] than the first dose, we’re seeing more than double the impairment,” King said in the release.